Method for producing the rotor of a drag vacuum pump and a rotor produced according to this method

ABSTRACT

A one-piece rotor ( 1 ) for a drag vacuum pump ( 21 ) is designed, at least in sections, as a turbomolecular vacuum pump with rotor blades ( 5 ) and stator blades ( 9 ), The rotor ( 1 ) has a hub ( 2 ) whose peripheral surface supports the pump structures. The rotor-side pump structures include, at least in sections, blades ( 5 ), which are arranged in rows ( 4 ) and which are formed from the surface of a blank by means of metal cutting operations. The metal cutting operations include producing radial peripheral grooves ( 3 ) into which stator blade rows ( 9 ) engage when the pump is assembled. In order to simplify the machining of the rotor ( 1 ), another metal cutting operation provides the outer surface of the blank with one or more thread grooves ( 13 ).

The invention relates to a method for producing the rotor of a drag vacuum pump according to the characteristics of patent claim 1. Moreover, the invention relates to a rotor produced according to this method.

It is known to produce the individual blades of a rotor of a turbomolecular vacuum pump in that the outer surface of a cylindrical blank (preferably of aluminium) is provided with radial peripheral grooves and axially oriented grooves, such that blades are created in planes perpendicular with respect to the axis of rotation. In order to attain blades exhibiting an effective pumping action, each of the multitude of blades needs to be subsequently set. Generally the blades shall have differing angles of attack/setting angles depending on their distance with respect to the inlet. The known production method does not allow for further variations of the blade profiles.

Moreover, it is known to prepare the blades by milling these from the surface of a blank, such that subsequent setting will no longer be required. This manufacturing procedure involves long processing times, particularly since it is desirable that the blades of different blade rows exhibit differing blade profiles and/or angles of attack.

It is the task of the present invention to reduce the previously required processing times and thus the costs for manufacturing rotors for drag vacuum pumps.

In accordance with the invention this task is solved through the characterising features of the patent claims. The invention allows the formation of rows of blades exhibiting differing angles of attack or blade profiles in a simple manner through metal cutting operations. This can be achieved in that the pitch of the thread grooves is varied in accordance with the desired conditions. By applying the methods according to the invention the milling times may, in addition, be reduced to a minimum, respectively milling can be replaced completely by turning operations.

Further advantages and details of the present invention shall be explained with reference to the examples of embodiments depicted in the drawing figures and 1 to 9 ¹⁾. ¹⁾ Translator's note: The German text states “8” here whereas “9” would be more in line with the drawing figures. Therefore the latter has been assumed for the translation.

Depicted are in

drawing FIGS. 1 to 4 much schematised rotors, manufactured in accordance with the present invention, whereby the rotors in accordance with the drawing FIGS. 1 and 2 are depicted in their semi-finished state,

drawing FIGS. 5 to 7 rotors with greater detail, manufactured in accordance with the present invention, whereby the rotor in accordance with drawing FIG. 5 is depicted in its semi-finished state, as well as

drawing FIGS. 8 and 9 partial sections through drag vacuum pumps with rotors manufactured in accordance with the present invention.

In all drawing figures the rotor is in each instance designated with 1 and its hub with 2. In the instance of completed rotors at least a section of the hub 2 supports rows of blades 4 separated by peripheral grooves 3, whereby the individual blades are in each instance designated as 5. In the assembled state (drawing FIGS. 8 and 9)²⁾ the rows of stator blades 9 engage in the peripheral grooves 3. The rotation of the rotor 1 effects the desired pumping of gases from the suction side 11 to the delivery side 12 of the rotor 1. ²⁾ Translator's note: The German text states “(drawing FIGS. 7 and 8)” here whereas “(drawing FIGS. 8 and 9)” would be more in line with the drawing figures; Therefore the latter has been assumed for the translation.

Drawing FIGS. 1 to 3 depict the manner in which a rotor 1 can be manufactured according to the present invention. Initially a, for example, cylindrical blank is provided either with thread grooves 13 (drawing FIG. 1) or with radial peripheral grooves 3 (drawing FIG. 2). After this step there is created in each instance the hub 2 of the rotors 1. The hub 2 according to drawing FIG. 1 carries one or several thread ridges 14, the hub 2 according to drawing FIG. 2 carries peripheral radial ridges 15.

Thereafter the rotor 1 according to drawing FIG. 1 is provided with the peripheral grooves 3, and the rotor 1 according to drawing FIG. 2 is provided with thread grooves 13. Thus in the instance of both methods the rotor 1 according to drawing FIG. 3 is created. On the hub 2 there remain blade rows 4 separated by the peripheral grooves 3. The profiles (width, length, cross-section) and the angles of attack of the blades 5 of a row of blades 4 depend on the width and the depth of the adjacent grooves 3, 13 as well as on the pitch of the thread grooves 13 at the level of the respective row of blades 4.

Drawing FIG. 4 depicts a rotor 1 which exhibits along its entire height thread grooves/ridges 13, 14. Only at its upper section are radial peripheral grooves 3 provided in addition. Through these measures, a one-piece rotor 1 for a drag vacuum pump is created, which is designed section-wise (on the intake side) as a turbomolecular pump and (on the delivery side) as a molecular pump (Holweck pump). From drawing 4 it is finally apparent that the pitch and above all the changes in pitch for the thread ridges 14 can be selected freely so that the pumping properties may be adapted precisely to the pressures prevailing at each point of the pumping channel.

Drawing FIGS. 5, 6 and 7 depict a rotor 1 in which the thread ridges 14 exhibit a constant pitch across the entire height of said rotor. Drawing FIG. 5 depicts the rotor 1 in its semi-finished state; it exhibits only thread ridges 14, respectively thread grooves 13. Drawing FIGS. 6 and 7 depict various views (drawing FIG. 6 side view, drawing FIG. 7 a view at an angle from below) of the finished rotor 1. After manufacturing of the thread grooves 13, the radial peripheral grooves 3 have been manufactured by turning.

Drawing FIG. 8 depicts a sectional view through the active pumping area of a turbomolecular pump 21. Stator blades 9 engage in the radial peripheral grooves 3 of the rotor 1 manufactured in accordance with the present invention. A cylindrical stator 22 with stator rings and blade rings serves, in a known manner, the purpose of supporting the stator blades 9. The depth of the peripheral grooves 3 decreases from the intake side 11 towards the delivery side 12. The same applies correspondingly for the length of the effective pumping blades of the row of blades 9. The result is a pumping cross section which decreases from the intake side towards the delivery side. The method in accordance with the present invention allows to manufacture, in a simple manner, a rotor 1 with the pumping properties described or also with other pumping properties.

In the embodiment according to drawing FIG. 9, only the intake section of the pump 21 is designed by way of a turbomolecular pump. The section on the delivery side is equipped with thread grooves/ridges 13, 14 with their width/height reducing towards the delivery side. Jointly with the inner surface of the stator 22 said section on the delivery side forms a Holweck pump. Also indicated is a third pumping stage 23, located downstream of the Holweck pumping stage of the rotor 1. Said third pumping stage comprises a thread 24 sunk into the stator 22, whereby said third pumping stage forms a further Holweck stage with the cylinder 25 affixed to the rotor 1. 

1. A method for producing a one-piece rotor for a drag vacuum pump which is designed, at least in sections, as a turbomolecular vacuum pump with rotor blades and stator blades, the rotor having a hub whose peripheral surface supports rotor-side pump structures, which rotor-side pump structures include, at least in sections, blades which are arranged in rows and which are formed from the surface of a blank by means of metal cutting operations, the metal cutting operations comprising: producing radial peripheral grooves into which stator blade rows engage when the pump is assembled; and in another metal cutting operation, providing the outer surface of the blank with one or more thread grooves.
 2. The method according to claim 1, wherein the thread grooves are produced first by milling and thereafter the peripheral grooves are produced by turning.
 3. The method according to claim 1, wherein the thread grooves and the peripheral grooves are both produced by turning.
 4. The method according to claim 1, wherein the peripheral grooves are produced first and thereafter the thread grooves are produced.
 5. A rotor manufactured according to the method of claim 1, wherein the thread grooves and the peripheral grooves form rotor blades.
 6. The rotor according to claim 5, wherein the thread grooves extend over the entire height and the peripheral grooves are section-wise.
 7. The rotor according to claim 5, wherein a depth of the peripheral and thread grooves decreases at least in sections from an intake side towards a delivery side of the rotor.
 8. The rotor according to claim 5, further including: a coaxially arranged cylinder on a delivery side.
 9. A vacuum pump with the rotor produced according to the method of claim
 1. 10. A method of producing a rotor for a vacuum pump comprising, in a cylinder blank in any order: cutting a series of spiral grooves; and cutting a series of peripheral grooves; such that a plurality of peripheral rows of blades are defined with the blades in each row angularly displaced form an adjacent row.
 11. The method according to claim 10 wherein a depth of at least one of the peripheral and spiral grooves varies axially along the blank.
 12. A rotor produced in accordance with the method of claim
 10. 